1. Field of the Invention
The present invention relates to an image processing apparatus, an image forming apparatus, and a computer-readable recording medium storing an image processing program. More particularly, it relates to a technology for preventing copying of a document image to which a special pattern for preventing copying is embedded.
2. Description of the Related Art
Conventionally, as a method for preventing copying of a confidential document and the like, there has been known a method of using a pattern image which causes warning characters to appear if the confidential document is copied with a copying machine. Creating a document with use of such pattern image has a psychological effect for preventing unfair copying, and makes it possible to distinguish an original and a copy.
However, although the method using the pattern image has a psychological effect for preventing unfair copying, it cannot physically prevent copying, and a leakage of information cannot be prevented completely. Therefore, as disclosed in Japanese Patent Unexamined Publication No. 2004-274092, there has been proposed a copying machine having a copy guard function for preventing a leakage of document information. According to such copying machine, a special pattern is detected from image data read from a document. If the special pattern is detected, copying of a document is prohibited, or a predetermined breaking pattern is printed out without printing a document.
Further, according to technologies disclosed in Japanese Patent Unexamined Publication No. 2006-173757 and Japanese Patent Unexamined Publication No. 2006-229709, in a case where a special pattern is detected from a document image, a breaking pattern is applied to the document image in halfway and then printed, or a blank image is outputted or transmitted, so that normal copying or reading is prevented.